1. Field of the Invention
The invention relates to liquid crystal display devices and somewhat more particularly to a method of producing such devices with an orientation layer therein.
2. Prior Art
Methods of producing liquid crystal display devices comprised of two carrier plates which enclose a liquid crystal layer therebetween and carry an electrically conductive coating on their respective surfaces facing one another and also carry an orientation layer superimposed on such electrically conductive coatings are known. For example, German Offenlegungsschrift 22 38 429 suggests such a production technique wherein the orientation layer is generated from a silane compound having an alkyl radical and a hydrolyzable group.
Silanization is one of the few orientation techniques which has proceeded beyond the experimental stage and achieved practical significance. Silane layers are relatively stable and adhesive, provide defined liquid crystal textures or alignments and are relatively simple to produce, in comparison with other suggested alignment techniques, such as oblique vapor-deposition. With silanization, one need only to dissolve a select silane material in water, apply the solution to a substrate and thereafter dry the applied layer. However, this simple fabrication technique is not of particular significance when one considers the overall liquid crystal carrier plate coating: generally, a carrier plate is comprised of four layers, a protective layer, a conductive layer, an insulation layer and an orientation layer. In this sequence, the production of a conductive layer involves the greatest amount of time and work, because one must first generate such layer via a CVD (chemical vapor deposition) technique or via a sputtering technique and then structure the resultant layer in an etching process.
Of course, liquid crystal carrier plates can be constructed without separate orientation layers by adding certain surface-active substances to the liquid crystal layer so as to influence liquid crystal alignment or one can influence the conductive or protective layers in a specific manner so as to attain a defined liquid crystal texture. However, as experience has shown, attempts in this direction have not let to satisfactory results.